北京清洁区大气颗粒物污染特征及长期变化趋势

Study on Atmospheric Particles and Their Long-term Trend in Beijing Cleaning Area

清洁对照区表征了区域环境的影响,是全面评价城市大气环境质量变化的基础.本研究分析了北京清洁区定陵不同粒径颗粒物质量的历史监测数据,包括1980～2009年大气降尘、1991～2009年总悬浮颗粒物(TSP)、2000～2009年可吸入颗粒物(PM10).结果表明,北京清洁区大气颗粒物总体呈下降趋势,年际短期变化受沙尘天气影响较大.30年来降尘量明显下降,主要缘于北京及周边环境保护治理和生态环境的改善;叠加沙尘天气的影响降尘量呈现5～6 a的波动周期.TSP和PM10浓度起伏较大,但整体呈下降趋势.TSP浓度1990年代中后期较稳定,而2000年以来受沙尘影响有较大起伏.TSP中Pb和苯并(a)芘比例近20年来总体呈上升趋势.说明定陵大气颗粒物受自然源影响逐渐减弱,而受区域城市人为源影响有所增加.分析发现颗粒物粒径越大,季节变化越显著,局地特征越明显;反之,区域特征显著.

Observational data in clean area provides important references for evaluating environmental impact both from natural and anthropogenic sources.Atmospheric particulate matter of different size were closely examined using dustfall data during 1980-2009,TSP data during 1991-2009 and PM10 data since 2000 at Dingling station（DL）,which was located in the clean area of Beijing.It was shown that dustfall amount at DL was on decrease in the last 30 years,by reasons of anthropogenic emission control and ecological environment improvement;meanwhile there was a 5-6 years’cycle of variation in yearly dustfall amount partly caused by dust storms.Similarly TSP and PM10 concentrations changed greatly but had a decreasing trend since 2000.Furthermore,the ratios of Pb and BaP in TSP at DL,namely Pb/TSP and BaP/TSP,were analyzed for anthropogenic influence.It was proved that the ratios were increasing and there was stronger influence of regional pollutant transport from urban areas.Lastly,it was also found that the coarser atmospheric particles were,the stronger their seasonal fluctuations in mass were,which were mainly affected by local sources rather than regional,and vice verse.